There is increasing evidence for the existence of a family of tumor suppressor genes that are involved in different cancers. Using a technique known as microcell-mediated chromosome transfer, the Laboratory of Molecular Carcinogenesis, in collaboration with Dr. Mitsuo Oshimura (Tottori University, Japan), has mapped tumor suppressor genes involved in human and rodent cancers to chromosome 1 (endometrial cancer, fibrosarcomas), chromosome 3 (renal cancer, lung cancer), chromosome 6 (endometrial cancer), chromosome 7 (choriocarcinoma), chromosome 9 (endometrial cancer), and chromosome 11 (cervical cancer, Wilms' tumor, rhabdomyosarcoma, lung cancer, fibrosarcoma). To map tumor suppressor genes for lung adenocarcinomas, we have introduced various normal human chromosomes into the A549 tumor cell line by microcell-mediated chromosome transfer to test which chromosomes had the ability to suppress tumorigenicity. These results indicate that chromosome 3 and 11 can suppress the tumorigenicity of A549 lung adenocarcinoma cells. Previous studies using somatic cell hybridization of highly metastatic and non-metastatic rat prostatic cancer cells demonstrated that the resultant hybrids were non-metastatic if all of the parental chromosomes were retained. Somatic hybrid segregants which underwent non-random chromosomal losses reexpressed high metastatic ability. These results demonstrated that there are gene(s) whose expression can suppress metastatic ability of prostatic cancer cells. To identify the location of homologous gene(s) in the human, specific human chromosomes were introduced into highly metastatic rat prostatic cancer cells using the microcell-mediated chromosome transfer. Introduction of human chromosome 11 into highly metastatic rat prostate cancer cells results in suppression of metastatic ability without suppression of the in vivo growth rate or tumorigenicity of the hybrid cells. Spontaneous deletion of portions of human chromosome 11 in some of the clones delineated the minimal portion of human chromosome 11 capable of suppressing prostatic cancer metastases. A candidate gene for this metastasis suppressor was isolated.